多层水平气流带式干燥机的数学模型

根据干燥传质传热学原理和干燥动力学特性，建立了水平气流带式干燥机干燥过程的数学模型。该模型可以预测干燥机合理的通风道高度、带翻转最佳时间和热风风速等。为优化多层带式干燥机的结构或设计新的水平气流带式干燥机提供了理论依据。     

穿流气流带式干燥机设计与应用

一、概述 穿流气流带式干燥机主要由头部、物料成形机构、若干干燥单元、出料装置、网带运行机构等组成。它采用强制通风干燥法。由于热风和湿物料的接触面积大,既有对流传热,又有辐射传热,干燥热强度大。同时,因湿物料内部水汽排出的途径较短,因此具有较大的干燥速度。 本机能够连续操作,湿物料直接或经过物料成形机构分布到多孔网带运行机构上,     

真空冷冻干燥过程的模拟研究

在升华干燥阶段应用传热传质理论对 URIF模型进行了改进与完善 ,在解吸干燥阶段假设结合水的脱除随物料温升的变化率为常数 ,建立冷冻干燥模型 ,通过解析求解 ,得出了冷冻干燥过程时间的解析表达式 ,在工程应用中预测冻干时间十分方便。还分析了干燥室压力、物料厚度对冷冻干燥时间的影响。     

国内专利文摘

国内专利文摘Ｉｎｔ．Ｃｌ．６Ｆ２６Ｂ１７／２０公开号ＣＮ１１０６５２８Ａ发明名称全效干燥机发明人陈启松一种全效干燥机，适合于用蒸汽加热来干燥物料。该机主要由蒸汽喷射泵、夹套和干燥室３大部件组成。高温高压蒸汽喷射泵喷射后，产生真空作用，将干燥室内物料蒸...     

微波真空干燥工艺参数对猕猴桃切片品质的影响

微波真空干燥技术是在真空条件下利用微波能对物料进行干燥加工的一项新技术,本实验以猕猴桃切片为研究对象,以干制品复水率、维生素C含量以及干燥时间为指标,在单因素试验的基础上,通过3因素3水平的二次回归正交试验,研究了微波功率、物料厚度、干燥室压力对猕猴桃切片干燥特性的影响。结果表明：在微波功率为800W、切片厚度为4mm、干燥室压力为0．04MPa的条件下,微波真空干燥猕猴桃切片的干制品质量最好,确定了猕猴桃切片微波真空干燥较优工艺参数条件。     

膏糊状物料气流对流干燥试验研究

以分子筛滤饼作被干燥物料,模拟带式干燥机进行了干燥试验研究。考察了气流速度、温度以及干燥时间对物料干燥效果的影响,并与烘箱干燥试验数据进行对比。结果表明:气流速度越高,干燥温度越高,干燥后物料的水分含量越低;带式气流干燥机干燥时间短,处理量大,可以连续操作,干燥效果明显优于箱式干燥器,可以作为膏糊状物料的干燥设备。     

搅动型真空盘式干燥机

<正> ①英国欧洲文特公司为满足医药、化学和食品工业的需要而设计开发了一种该干燥器尤其适用于热敏性材料的处理。②用以混合和干燥的。③搅动型式真空盘式干燥机。 该真空盘式干燥机采用不锈钢结构的无缝隙机械密封,干燥室的进出口很简便,上盖能够自动升降或转到吊柱侧面。为消除粉尘公害,真空系统能有助于产品通过承载口     

用于市政污泥干化的干燥机选型及设计计算

针对市政污泥的干燥特性与干化过程中出现的粘滞区现象,对5种常用干燥设备的功能、物料适用性等进行分析,确定卧式桨叶式干燥机是最适合干燥市政污泥的设备,并以100 t/d市政污泥处理量为例进行了干燥机的选型设计计算。最后推荐一种新型薄层干燥机作为后续优化选型时的备选设备。     

高湿物料真空连续复合管束烘干设备研制初步探讨

从分析影响烘干设备干燥效果的烘干时间、加热温度、运行距离、物料与加热系统的接触面积入手，研制出高湿物料真空连续复合管束烘干设备。干燥主机采用三个不同直径的同心圆筒组成多级干燥室，各个干燥室内设有一定数量的加热管束，利用真空连续干燥、热能按需分配的原理，延长物料在干燥主机内的烘干时间、运行距离，加大物料与加热系统的接触面积，提高烘干设备的空间利用率。从而有效踺提高了烘干效率，降低烘干成本，改善了物料品质；改变了传统管束烘干设备采用一级干燥室的空间利用率低、热能不被充分利用的局面。     

自动真空履带干燥机在制药行业中的应用

介绍了自动真空覆带干燥机的结构、工作原理、特点及控制系统的总体设计,将其应用于中药浸膏干燥,实现了干燥温度、真空压力、干燥速度和干燥物料含水率稳定的目标.     

CONTINUOUS VACUUM DRYER FOR ENERGY SAVING

A continuous vacuum dryer for energy saving has been developed in order to produce dried foods without heat denaturation in the products. This drying method is suitable for heat sensitive I and highly viscous foods and can dry to 1 to 4% in moisture content with good quality at around 40°C in product temperature andin 5 -10 min a drying time. Feed material with high viscosity has to I have uniform distribution on the belt in the vacuum chamber to I keep a constant drying for which a special feed nozzle has been developed after considerabl~ testing. Heat transfer on the wet material in the dryer has occurred by both conduction and radiation because of the design so that the thermal efficiency in     

DYNAMIC SIMULATION AND CONTROL OF CONVEYOR-BELT DRYERS

Abstract

The dynamic behavior of conveyor-belt dryers involving externally controlled heat and mass transfer phenomena has been studied via digital simulation. The investigation concerned an industrial dryer used for the moisture removal from wet raisins. The dryer consisted of three drying chambers and a cooling section, all involving the same conveyor belt. For each chamber, perfect temperature control was assumed for the drying air temperature, while its humidity was left uncontrolled. The effect of material temperature and moisture content at the entrance of the dryer and the drying air temperature on material temperature and moisture content at the exit of the dryer and the corresponding drying air humidity, have been explored by step forcing the disturbance and manipulated variables in the non-linear dryer model simulator. Results showed that material moisture content at the exit of the dryer is greatly affected by material moisture content at the entrance as well as by the drying air temperature. Reliable transfer functions for each process module were obtained by fitting several transfer function models on the simulated data using a least-squares approach. It was found that when input material moisture content could be instantly measured, the system responded slowly enough so that excellent control could be achieved for material moisture content at the exit of each chamber. In this case a Pi-feedback cascade temperature controller was used. When a 15 sec delay measuring sensor was introduced, poor performance was observed. A simplified lead-lag feedforward controller, added to the system, in conjunction with the primary Pi-feedback cascade controller, resulted in good control performance of the delay sensor system.     

DYNAMIC SIMULATION AND CONTROL OF CONVEYOR-BELT DRYERS

The dynamic behavior of conveyor-belt dryers involving externally controlled heat and mass transfer phenomena has been studied via digital simulation. The investigation concerned an industrial dryer used for the moisture removal from wet raisins. The dryer consisted of three drying chambers and a cooling section, all involving the same conveyor belt. For each chamber, perfect temperature control was assumed for the drying air temperature, while its humidity was left uncontrolled. The effect of material temperature and moisture content at the entrance of the dryer and the drying air temperature on material temperature and moisture content at the exit of the dryer and the corresponding drying air humidity, have been explored by step forcing the disturbance and manipulated variables in the non-linear dryer model simulator. Results showed that material moisture content at the exit of the dryer is greatly affected by material moisture content at the entrance as well as by the drying air temperature. Reliable transfer functions for each process module were obtained by fitting several transfer function models on the simulated data using a least-squares approach. It was found that when input material moisture content could be instantly measured, the system responded slowly enough so that excellent control could be achieved for material moisture content at the exit of each chamber. In this case a Pi-feedback cascade temperature controller was used. When a 15 sec delay measuring sensor was introduced, poor performance was observed. A simplified lead-lag feedforward controller, added to the system, in conjunction with the primary Pi-feedback cascade controller, resulted in good control performance of the delay sensor system.     

高气密耐磨关风器与低温真空干燥简仓

关风器是气力输送、真空输送系统中不可或缺的设备，有旋转阀、星型给排料机、密闭旋转叶片给排料机等多种名称。减小关风器漏气量、延长使用寿命是本产品的难点；减小叶轮工作状态各封闭腔体压力差。选用复合耐磨自润滑材料是达到关风器漏气量小、使用寿命长的有效途径。真空干燥筒仓有多种结构，但适合做大产量连续干燥的不多。研制一种工作状态设备外壳静止、仓内单位容积换热面积大的筒仓，有利于降低设备制造总成本。     

Dynamic Modeling and a Parametric Study of an Indirect Solar Cabinet Dryer

A dynamic mathematical model for drying of agricultural products in an indirect cabinet solar dryer is presented. This model describes the heat and mass transfer in the drying chamber and also considers the heat transfer and temperature distribution in a solar collector under transient conditions. For this purpose, using conservation laws of heat and mass transfer and considering the physical phenomena occurring in a solar dryer, the governing equations are derived and solved numerically. The model solution provides an effective tool to study the variation of temperature and humidity of the drying air, drying material temperature, and its moisture content on each tray. The predicted results are compared with available experimental data. It is shown that the model can predict the performance of the cabinet solar dryer in unsteady-state operating conditions well. Furthermore, the effect of some operating parameters on the performance and efficiency of dryer is investigated and compared with selected published data.     

Control of Drying Process in Mechanically Spouted Bed Dryer

The continuously operated Mechanically Spouted Bed (MSB) dryer of high evaporative capacity can be advantageously used to produce fine powder from paste-like materials, slurries, suspensions and sludges. Due to the thin layer formed on the surface of the spherical inert particles intensive heat and mass transfer occur and the drying process takes place in the constant rate period. Steady state drying conditions can be achieved when the total operational time of partial processes of inert bed drying does not exceed the cycle time of the inert particles.

A laboratory scale MSB dryer has been equipped with a computerised measuring, data acquisition and control system. In the knowledge of the hydrodynamic characteristics of the MSB and giving the enthalpy and mass balances over the dryer a calculation method has been developed for control of drying process.     

Control of Drying Process in Mechanically Spouted Bed Dryer

ABSTRACT

The continuously operated Mechanically Spouted Bed (MSB) dryer of high evaporative capacity can be advantageously used to produce fine powder from paste-like materials, slurries, suspensions and sludges. Due to the thin layer formed on the surface of the spherical inert particles intensive heat and mass transfer occur and the drying process takes place in the constant rate period. Steady state drying conditions can be achieved when the total operational time of partial processes of inert bed drying does not exceed the cycle time of the inert particles.

A laboratory scale MSB dryer has been equipped with a computerised measuring, data acquisition and control system. In the knowledge of the hydrodynamic characteristics of the MSB and giving the enthalpy and mass balances over the dryer a calculation method has been developed for control of drying process.     

A Simulation Model for Heat Pump Dryer Plants for Fruits and Roots.

Dryer design requires food properties, drying rate and mass-heat transfer coefficients. These values change continuously during drying due to changes in food fractions, particularly the water fraction. The high energy demand and costs allied to inefficient devices, creates a great need for new processing equipment. Along these guide-lines, several heat pump drying research projects were established at the Norwegian University of Science and Technology. The heat pump dryer provides high quality final product as its drying conditions can be controlled. Its efficiency and non-polluting operation come from closed air-refrigerant circuits and from its ability to fully recover the latent heat of moist air as it exits the drying chamber. Most of the above features are quite the opposite of the conventional dryer characteristics. Several experiments were made on heat pump drying of fruits and roots at temperatures from -22.5 to 40°C to obtain data and correlations on thermophysical properties, specific enthalpy and rehydration. Also, tests were done on drying rate, moisture content, drying constant, effective mass diffusivity and heat and mass transfer equations. The next important phase is the development of a simulation model to predict the performance and characteristics of the heat pump dryer plant. The objectives of the present work are to develop and lo test a heat pump dryer simulation model. The simulation provides results on the characteristics of both plant and components which are integrated by heat and mass transfer equations. The program has menus with click-on icons, input and output pop-up dialogue boxes. The usual commands such as, file-open, file-save, edit-delete are available in this program simply called Hpdryer. The model contains moist air psychrometric. natural and conventional refrigerant property libraries. Ammonia is a time-tested, self-alarming and natural refrigerant. It has been used extensively in the past, and it has better thermodynamic and transport properties than halocarbons. Safety is easily attained by design and its restrictive standards have helped increase its use in several countries. There are 36 ammonia installations in Norway and in the United Kingdom, including a drying plant. Ammonia has zero Odp, zero Gwp and the recent R&D has led to viable small-sale heat pump plants. Ammonia and dichlarodifluoromethane refrigerants were used in the test cases simulated by Hpdryer madel.     

A Simulation Model for Heat Pump Dryer Plants for Fruits and Roots.

ABSTRACT

Dryer design requires food properties, drying rate and mass-heat transfer coefficients. These values change continuously during drying due to changes in food fractions, particularly the water fraction. The high energy demand and costs allied to inefficient devices, creates a great need for new processing equipment. Along these guide-lines, several heat pump drying research projects were established at the Norwegian University of Science and Technology. The heat pump dryer provides high quality final product as its drying conditions can be controlled. Its efficiency and non-polluting operation come from closed air-refrigerant circuits and from its ability to fully recover the latent heat of moist air as it exits the drying chamber. Most of the above features are quite the opposite of the conventional dryer characteristics. Several experiments were made on heat pump drying of fruits and roots at temperatures from -22.5 to 40°C to obtain data and correlations on thermophysical properties, specific enthalpy and rehydration. Also, tests were done on drying rate, moisture content, drying constant, effective mass diffusivity and heat and mass transfer equations. The next important phase is the development of a simulation model to predict the performance and characteristics of the heat pump dryer plant. The objectives of the present work are to develop and lo test a heat pump dryer simulation model. The simulation provides results on the characteristics of both plant and components which are integrated by heat and mass transfer equations. The program has menus with click-on icons, input and output pop-up dialogue boxes. The usual commands such as, file-open, file-save, edit-delete are available in this program simply called Hpdryer. The model contains moist air psychrometric. natural and conventional refrigerant property libraries. Ammonia is a time-tested, self-alarming and natural refrigerant. It has been used extensively in the past, and it has better thermodynamic and transport properties than halocarbons. Safety is easily attained by design and its restrictive standards have helped increase its use in several countries. There are 36 ammonia installations in Norway and in the United Kingdom, including a drying plant. Ammonia has zero Odp, zero Gwp and the recent R&D has led to viable small-sale heat pump plants. Ammonia and dichlarodifluoromethane refrigerants were used in the test cases simulated by Hpdryer madel.